Remove the unused class SingleContextManager

pkg/analysis_server/lib/src/server/driver.dart

Index: pkg/analysis_server/lib/src/server/driver.dart
diff --git a/pkg/analysis_server/lib/src/server/driver.dart b/pkg/analysis_server/lib/src/server/driver.dart
index 30215da4657b28f4546edd730966b80b0368466c..87d4792a6459b1f5e5c631f4ffd8a629948697f4 100644
--- a/pkg/analysis_server/lib/src/server/driver.dart
+++ b/pkg/analysis_server/lib/src/server/driver.dart
@@ -307,14 +307,6 @@ class Driver implements ServerStarter {
   ResolverProvider packageResolverProvider;
 
   /**
-   * If this flag is `true`, then single analysis context should be used for
-   * analysis of multiple analysis roots, special files that could otherwise
-   * cause creating additional contexts, such as `pubspec.yaml`, or `.packages`,
-   * or analysis options are ignored.
-   */
-  bool useSingleContextManager = false;
-
-  /**
    * The plugins that are defined outside the analysis_server package.
    */
   List<Plugin> _userDefinedPlugins = <Plugin>[];
@@ -453,8 +445,7 @@ class Driver implements ServerStarter {
         diagnosticServer,
         serverPlugin,
         fileResolverProvider,
-        packageResolverProvider,
-        useSingleContextManager);
+        packageResolverProvider);
     httpServer = new HttpAnalysisServer(socketServer);
     stdioServer = new StdioAnalysisServer(socketServer);
     socketServer.userDefinedPlugins = _userDefinedPlugins;